Should You Be Lifting Heavy or Light Weights to Build Muscle? Here’s the science.

There is so much conflicting advice on how to approach strength training, and especially lifting heavy weights. Especially more recently, as influencers on social media and others have started touting the benefits of heavy weightlifting over other types of training. When you see all these people lifting heavy, it’s easy to assume that heavier equals better or more progress. It is confusing. People aren’t sure if they need to do super heavy weights to gain a benefit, or if lighter weights will give them the same or similar muscle benefits and gains. The truth is that lifting heavier and lighter both have benefits, and in fact, they aren’t much different in their results.

There are many studies showing that lifting heavy weights and lifting light weights have no real differences. In fact, a study published by researchers at McMaster university in Canada showed that doing more repetitions using lighter weights is just as effective at building muscle as was lifting heavy weights for fewer repetitions. They found that this was true so long as the people in the study lifted the weights to a point of fatigue.

“The science is clear about strength training,” says Dr. Jenni Bruning Brown, Fly Fitness Founder and trainer for over 20 years. “You can lift heavier or lighter weights, but you simply need to get to a point of muscle fatigue by the end of your workout or set, where you should feel pretty close to needing to stop.”  So, you can get the same benefits from training with light weights as you do with heavy ones if you push yourself to the point of muscle fatigue. 

In fact, another study was completed a few years ago that had similar results. They found that the amount of weight did not impact the outcome. That is, both light and heavy weights produced equal amount of muscle growth on all the study participants. A study which was a meta-analysis (a study that takes the results of multiple other studies and looks at them as a whole) found the same thing—that lifting heavy weights and light weights leads to similar results. 

Dr. Bruning Brown says that studies like this are a wake-up call to those that think you exclusively must lift heavy (heaviest weight and below 10 repetitions) to gain muscle. In fact, the research and science are encouraging for people who have joint issues or those who think they can’t build muscle using lighter weights. The truth is, while lifting heavy weights can be beneficial for those looking to build size or bulk, any form of strength training can give you benefits if you push yourself to the point of fatigue. 

Dr. Bruning Brown says the results are clear: “you get the same results in building lean muscle and can change the shape of your body by lifting heavier or lighter weights. You will gain muscle equally from either one, but you need to challenge yourself, and continue build on your progress.” 

If you love lifting heavy, she says, go for it, just know that it isn’t the only way for you to make strength gains or build lean muscle.